Thomas Rhett is the first to admit his new love song "Unforgettable" is not ripped from his and his wife's personal life. The song did get her stamp of approval, however.

Ashley Gorley, Shane McAnally and Jesse Frasure helped Rhett write "Unforgettable," the second single from the singer's third studio album expected this fall. It's a mid-tempo love song that was written on the tour bus. Every song Rhett helped write on the upcoming album was penned on his tour bus, he says.

"I remember Shane talking about how a lot of couples are talking about 'Hey, do you remember the day we met,'" the singer recalls.

"We kind of told the story of, basically, it could be a boyfriend or it could be a husband, describing to his wife all these amazing details that she probably thought he’d forgotten about."

"I can smell your perfume, girl that night was just like you / Unforgettable," Rhett sings at the chorus, before adding "From your blue jeans to your shoes girl that night was just like you / Unforgettable."

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Rhett tells the Tennessean that his wife Lauren approved the song. She's put her stamp of approval on many of his No. 1 hits.

"If you listen to it hardcore enough, it might make you tear up a little bit," he tells the Nashville newspaper. "Especially if you're in love with somebody."

The song is the second single from the third studio album, and the third he's talked about in some detail. Earlier this year Rhett told Taste of Country about a song called "Life Changes," saying, "Basically it goes from me being in college to me being here now and how drastically my life has changed in the last five or six years. And (adopted daughter) Willa being a huge part of that."

The couple are also preparing for the birth of a baby girl in August.

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